In certain applications it is desirable to process luminance and chrominance signals in a combined or composite form and in other applications it may be desirable to maintain the signals in a separated or component form. For example, conventional consumer video cameras and video cassette recorders provide video output signals in composite form in which luminance and chrominance signals are combined so as to form a single "composite" video signal. Advantageously, the composite form of color video transmission only requires a single coaxial cable for connection to a monitor or recorder input. For higher quality consumer applications it is common to provide video output signals in a separated or "component" format in which the luminance and chrominance components are not mixed but rather are available separately. Such a transmission format is used in so-called "SVHS" (super VHS) consumer products.
In certain applications it is desirable to be able to convert video signals from component to composite form. One such application is described by Klink in U.S. Pat. No. 5,296,921 entitled TWO PORT NETWORK WITH SHARED ELEMENTS FOR COMBINING AND FILTERING LUMA AND CHROMA COMPONENTS TO FORM COMPOSITE VIDEO SIGNAL which issued Mar. 22, 1995. In an example of the Klink apparatus, a two-port passive filter network is used to combine luminance and chrominance components within a picture in picture processor in such a manner as to suppress certain visual artifacts characteristic of the specific picture in picture processing described. The use of passive networks, however, precludes use of the combined signals in certain applications such as cases in which a power gain may be desired. The use of active networks heretofore has required relatively complex circuitry and particularly so where plural buffered outputs are required which may require different transmission gains at different outputs and which may be subjected to varying load impedances.